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Overburden Wells
Wells located in the valley bottoms and flatlands of the British Columbia Southern Interior are often completed in overburden. Overburden consists of the unconsolidated material starting at the surface made up of gravels, sands, silts, clays and glacial till, a mix of material, deposited during glaciation. Wells drilled in overburden are usually exploratory as deposits can change substantially, even over a short distance.
Wells are drilled using welded steel casing advanced through the overburden using air powered percussion methods and cuttings are cleaned out of the casing as drilling progresses by air lifting. The upper portion of the casing is sealed to prevent surface water contamination. Once a suitable producing formation or aquifer is encountered, sampling of the formation is done to provide material for a sieve analysis to determine the optimum size of screen opening required to maximize flow, prevent plugging, and allow sand-free pumping. With screening positioned near the bottom of the casing, the well is developed, using compressed air, a step which removes the finer material from the formation through the screen, enlarging water flow passages, and maximizing production. Chlorination, capping, and tagging are the final steps in completing wells, ready for pumping. Cascade’s well logs are all entered into a computer database dating back to 1982 which provides rapid retrieval and access for well planning.
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